Actual operating time indicator

ABSTRACT

An actual operating time indicator includes: a lifting motor for lifting a load up/down; a power detection unit for detecting an input power based on a current and a voltage supplied to the motor, and converting the input power into a first voltage proportional to the input power; a voltage-to-periodic pulse conversion unit connected to the power detection unit for receiving the first voltage and converting the first voltage into the periodic pulse proportional to the first voltage; a counter unit connected to the voltage-to-periodic pulse conversion unit for counting and integrating the periodic pulse to obtain an integrated power; and a display operatively connected to the counter unit for indicating the integrated power as an actual operating time of the motor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an actual operating time indicator,more particularly, it relates to an actual operating time indicator forindicating an actual operating time of a hoist apparatus on a digitaldisplay. The present invention is advantageously used for an electrichoist apparatus which lifts a load up/down by using a motor, forexample, a three-phase induction motor.

2. Description of the Related Art

A hoist apparatus for lifting a load up/down is widely used in variousfields, for example, in a factory, a warehouse, construction and thelike. There are mainly three types of hoist apparatus from a viewpointof a motive power source, i.e., a compressed air type, an electric type,and a manual type. Although these types have individual advantages, theelectric type is the most popular because this type has various meritsfrom a viewpoint of cost/performance. The present invention relates tothe electric hoist apparatus.

In general, an electric hoist apparatus has two motors, i.e., one is alifting motor for lifting a load up/down, and the other is a travellingmotor for moving the hoist apparatus in a traverse direction on a beam.The lifting motor is usually formed by a three-phase induction motorbecause of a simple/firm structure, relatively low cost and high power.

The lifting motor is defined by at least a rating load indicating aweight of a load in normal use, output power at the rating load, ratingtime for indicating a range of continuous use time, and a test load forindicating a maximum load.

In the above mentioned various fields, the hoist apparatus may betemporarily used in an overload state or over-time state. Accordingly,it is necessary to obtain precise data which can be utilized formaintenance of the apparatus after use for a certain time period. Forexample, it is necessary to precisely measure a relationship between aload and an operating time from a start point of use.

There are two main methods for indicating the actual operating time in aconventional art. That is, the actual operating time of the hoistapparatus is displayed by either an integrating wattmeter or a counter.However, the former merely indicates a so-called "total power-on time"for a certain period of time, and the latter merely indicates a numberof times the hoist apparatus is operated.

Accordingly, in the above conventional art, the influence of a loadduring actual use of the hoist apparatus is not considered, for example,in an overload state or over-time state, so that it is impossible toprecisely measure the actual operating time while taking the load intoconsideration.

Further, although the life span of a mechanism varies depending on theload during use, in the conventional art, the relationship between thelife span of the mechanism and the load when measuring the actualoperating time of the hoist apparatus is not considered. Accordingly, inthe conventional art, the data are insufficient for maintenance so thatit is impossible to efficiently maintain the hoist apparatus.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an actual operatingtime indicator enabling precise measurement of an actual operating timeof a hoist apparatus, particularly, a lifting motor for lifting a loadup/down.

In accordance with one aspect of the present invention, there isprovided an actual operating time indicator including: a lifting motorfor lifting a load up/down; a power detection unit for detecting aninput power based on a current and a voltage supplied to the motor, andconverting the input power into a first voltage proportional to theinput power; a voltage-to-periodic pulse conversion unit connected tothe power detection unit for receiving the first voltage and convertingthe first voltage into a periodic pulse proportional to the firstvoltage; a counter unit connected to the voltage-to-periodic pulseconversion unit for counting and integrating the periodic pulse toobtain an integrated power; and a display operatively connected to thecounter unit for indicating the integrated power as an actual operatingtime of the motor.

In a preferred embodiment, the actual operating time indicator furtherincludes a divider connected to the counter unit for dividing theintegrated power by a power rating which is equivalent to the inputpower per unit hour when lifting up a rated load.

In another preferred embodiment, the actual operating time indicatorfurther includes a BCD unit operatively connected to the counter unitfor converting a binary number into a decimal number to display theactual operating time on the display unit.

In accordance with another aspect of the present invention, there isprovided an actual operating time indicator, including: a lifting motorfor lifting a load up/down; a power detection unit for detecting aninput power based on a current and a voltage supplied to the motor,converting the input power into a first voltage proportional to theinput power, and further converting the first voltage into a secondvoltage which is converted based on a predetermined formula defined byrelationship between a rating load and a life span of a mechanism; avoltage-to-periodic pulse conversion unit connected to the powerdetection unit for receiving the second voltage and converting thesecond voltage into the periodic pulse proportional to the secondvoltage; a counter unit connected to the voltage-to-periodic pulseconversion unit for counting and integrating the periodic pulse toobtain an integrated power; and a display operatively connected to thecounter unit for indicating the integrated power as an actual operatingtime of the motor.

In another embodiment, the predetermined formula is expressed byLh∝(1/P)^(n) where, Lh is a life span of a mechanism, P is a weight of aload, and n is an integer determined by a material of the mechanism.

In still another embodiment, preferably, the integer "n" of the formulais given by a numeral "3" so that the second voltage is determined basedon the formula,

    Lh∝(1/P).sup.3

In still another embodiment, the power detection unit includes an inputvoltage conversion unit for obtaining the second voltage, and the inputvoltage conversion unit is formed by: a first calculation unit inputtingthe first voltage Vb and a rating voltage VaH which is given by thevoltage proportional to the rating input power of the lifting motorduring the high speed lifting up operation, and calculates the formula(Vb/VaH)² ; a second calculation unit inputting the first voltage Vb anda rating voltage VaL which is given by the voltage proportional to therated input power of the lifting motor during the low speed lifting upoperation, and calculates the formula (Vb/VaL)² ; the first voltagebeing given by half of the rating voltage VaH or VaL so that the formula(Vb/VaH or VaL)² is given by (1/2)² ; a selector for selecting either anoutput of the first calculation unit or an output of the secondcalculation unit; and a third calculation unit inputting the firstvoltage and either the voltage (Vb/VaH)² or (Vb/VaL)², calculatingeither the formula (Vb)×(Vb/VaH)², or (Vb)×(Vb/VaL)², and outputting theresult of the calculation as the second voltage.

In accordance with still another aspect of the present invention, theactual operating time indicator, includes: a lifting motor for lifting aload up/down; a power detection unit for detecting an input power basedon a current and a voltage supplied to the motor, and converting theinput power into a first voltage proportional to the input power; amicrocomputer connected to the power detection unit for receiving thefirst voltage and outputting an integrated power; and a displayconnected to the microcomputer indicating the integrated power as anactual operating time of the motor.

In still another embodiment, the microcomputer includes ananalog-to-digital converter, an input port, a central processing unit(CPU), a read only memory (ROM) for storing a basic program forcalculation by the CPU, a random access memory (RAM) for temporarilystoring a result of the calculation by the CPU, a backup memory, and anoutput port; wherein, the A/D converter converts the first voltage Vbinto a digital value, and further converts a rating voltage VaH or VaLinto a digital value;

the CPU calculates the following; first, digitized Vb/VaH or Vb/VaL;second, digitized (Vb/VaH)² or (Vb/VaL)² and third, digitizedVb×(Vb/VaH)² or Vb×(Vb/VaL)² ;

the CPU counts the result of the calculation and obtains the totalnumber of the count, and divides the total number of the count by aconstant (K) which 35 corresponds to an input power rating; and

the display indicates the result of the division as the actual operatingtime; where, the rating voltage (YaH or VaL) is given by the voltageproportional to the rating input power of the lifting motor during thehigh (low) speed lifting up operation.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a block diagram of an actual operating time indicatoraccording to a first embodiment of the present invention;

FIG. 2 is a block diagram of an actual operating time indicatoraccording to a second embodiment of the present invention;

FIG. 3 is a detailed block diagram of an input voltage conversion meansshown in FIG. 2;

FIG. 4 is another block diagram of an actual operating time indicatorshown in FIG. 2;

FIG. 5 is a flowchart for explaining an operation of a structure of FIG.4; and

FIG. 6 is a schematic view of a hoist apparatus and a control boxincluding an actual operating time indicator according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram of an actual operating time indicatoraccording to a first embodiment of the present invention. In FIG. 1, "M"denotes a three-phase induction motor used as the lifting motor andoperated by AC 200 (v) commercial power. Reference number 1 denotes apower detection unit including an ampere meter A, a volt meter V, and apower-to-voltage conversion unit 11. Reference number 2 denotes avoltage-to-periodic pulse conversion unit V/F, 3 denotes a counter forcounting periodic pulses, 4 denotes a divider, 5 denotes a BCD (binarycoded decimal) unit, and 6 denotes a display unit for indicating anactual operating time.

As shown in the drawing, the lifting motor M has three phases i.e., "T","S" and "R" phases. The ampere , meter A is connected in series to the Tphase, and the volt meter V is connected in parallel between the T and Sphases to detect the current and voltage applied to the lifting motor M.

The power-to-voltage conversion unit 11 is provided for obtaining afirst voltage "el" proportional to an input power W to the lifting motorM. As is known, the input power W of the lifting motor M can be obtainedby multiplying the current A by the voltage V and a power-factor sincethe power is alternating current.

That is, in the power-to-voltage conversion unit 11, the change of thecurrent A is converted to the change of a voltage V_(A) (not shown) byflowing the current A through a predetermined constant resistor (notshown), and the voltage V_(A) is multiplied by the voltage V using aknown multiplier (not shown) so that it is possible to obtain thevoltage "e1" proportional to the input power W to the lifting motor M.

The voltage-to-frequency conversion unit 2 is provided for convertingthe voltage "e1" from the power-to-voltage conversion unit 11 into aperiodic pulse "f". A known digital volt meter utilizesvoltage-to-frequency conversion. That is, the digital volt meter countsthe periodic pulses to obtain the voltage. This is because that theperiodic pulse obtained by the voltage-to-frequency conversion unit isproportional to the measured voltage. Accordingly, thevoltage-to-frequency conversion unit 2 outputs a periodic pulseproportional to the input power.

The counter 3 is provided for counting the periodic pulse "f" from thevoltage-to-frequency conversion unit 2. Accordingly, the total count ofthe counter 3 corresponds to the integrated power.

The divider 4 is provided for dividing the integrated power by a powerrating. The power rating is equivalent to the power per unit hour (i.e.,a unit power) when lifting up a rated load. As a result, since theintegrated power is divided by the unit power, it is possible to obtainthe "total power-on time" which is converted to the load rating. As isobvious, the "total power-on time" of the above is different from theconventional "power-on time", and it becomes the "total power-on time"taking the use of the hoist apparatus into consideration. Accordingly,it is possible to obtain precise data for maintenance.

The BCD unit 5 is provided for converting the binary 10 number from thedivider 4 into a decimal number to display the actual operating time onthe display unit 6.

FIG. 2 is a block diagram of an actual operating time indicatoraccording to a second embodiment of the present invention. The samereference numbers as used in FIG. 1 are attached to the same componentsin this drawing. Since the components 2 to 6 have already been explainedin relation to FIG. 1, the explanation will be omitted for this drawing.

The power detection unit 1' of this embodiment further includes an inputvoltage conversion unit 12. The input voltage conversion unit 12 isprovided for converting the voltage "e1" into a voltage "e2" taking thelife span of the mechanism into consideration as explained in detailbelow. That is, the voltage "e1" from the power-to-voltage conversionunit 11 is converted to the voltage "e2" based on a predeterminedformula indicating the relationship between the load and the life spanof the mechanism. Then, the voltage "e2" is sent to thevoltage-to-periodic pulse conversion unit 2, and the same processes asexplained in relation to FIG. 1 are performed in the components 3 to 6.

The basic concept of the input voltage conversion unit 12 will beexplained in detail below. That is, it is known that an element that hasthe greatest influence on the life span of the mechanism is the weightof the load. Further, in general, the relationship between the load andthe life span of the mechanism is expressed by the following formula,

    Lh∝(1/P).sup.n                                      (1)

where,

Lh is a life span of a mechanism,

P is a weight of a load, and

n is an integer determined by a material of the mechanism.

The integer "n" is defined in the Japanese Industrial Standard (JIS B8815 (electric chain-block)) and the European Machine ConveyanceAssociation (FEM). In these documents, the integer "n" is experimentallygiven by the numeral "3".

When "n" is "3", the formula (1) becomes as follows.

    Lh∝(1/P).sup.3                                      (2)

Accordingly, the input voltage conversion unit 12 of the presentinvention is formed based on the formula (2) as explained below.

FIG. 3 is a detailed block diagram of an input voltage conversion unitshown in FIG. 2. In FIG. 3, reference number 121 denotes a firstcalculation unit, 122 denotes a second calculation unit, 123 denotes athird calculation unit, and 124 denotes a selector.

Further, "H" denotes a high speed lifting operation of the lifting motorM, and "L" denotes a low speed lifting operation of the lifting motor M.In the present invention, the voltage VaH is given by a voltageproportional to the rated input power of the lifting motor at the highspeed, and the voltage VaL is given by the voltage proportional to therated input power of the lifting motor at the low speed. Still further,the voltage Vb corresponds to the voltage "el" from the power-to-voltageconversion unit 11.

The first calculation unit 121 inputs the voltage Vb and the voltageVaH, and calculates (Vb/VaH)². In this embodiment, assuming that thevoltage Vb is half of the voltage VaH, i.e., Vb=VaH/2, the formula(Vb/VaH)² is given by (1/2)², i.e., 1/4.

The second calculation unit 122 inputs the voltage Vb and the voltageVaL, and calculates (Vb/VaL)². Similarly, in this embodiment, assumingthat the voltage Vb is half of the voltage VaL, i.e., Vb=VaL/2, theformula (Vb/VaL)² is given by (1/2)², i.e., 1/4.

The selector 124 is provided for selecting either the high speed or thelow speed (HIGH/LOW) of the lifting up/down operation. In general, thisselector is switched by an operator from a control box shown in FIG. 6.As shown in the drawing, the selector switches either the output of thefirst calculation unit 121 or the output of the second calculation unit122.

The third calculation unit 123 inputs the voltage Vb and either thevoltage (Vb/VaH)² or (Vb/VaL)², and calculates the following formula.

    (Vb)×(Vb/VaH).sup.2, or                              (3)

    (Vb)×(Vb/VaL).sup.2                                  (4)

As mentioned above, when Vb=YaH (VaL)/2 the formula (3) is given byVaH×(1/2)³, and the formula (4) is given by VaL×(1/2)³.

As is obvious, the numeral "3" of the above corresponds to the integer"n" of the formula (1).

This means that, in the first embodiment in FIG. 1, although the inputpower having half of the rated power is converted to a voltage, in thesecond embodiment in FIG. 2, first, the input power having half of therated power is converted to 1/8 of the rated power, then the convertedinput power is converted to the voltage "e2" proportional to theconverted input power.

Accordingly, in the second embodiment, it is possible to obtain theactual operating time taking the actual use of the hoist apparatus intoconsideration.

FIG. 4 is another block diagram of an actual operating time indicatorshown in FIG. 2. The same reference numbers as used in FIGS. 1 and 2 areattached to the same components in this drawing. "M" denotes amicrocomputer. The microcomputer M includes an analog-to-digitalconverter (A/D), an input port (IP), a central processing unit (CPU), aread only memory (ROM), a random access memory (RAM), a backup memory,and an output port (OP). Based on these components, the microcomputerhas functions of the input voltage conversion unit 12, the counter 3,the divider 4 and the BCD unit 5. The ROM stores a basic program for thecalculation by the CPU, and the RAM temporarily stores the result of thecalculation by the CPU. The backup memory has a backup function for theRAM. The input port and the output port are provided as terminals. Theoperation of the CPU is shown in FIG. 5.

FIG. 5 is a flowchart for explaining an operation of the structure ofFIG. 4. In step S1, the A/D converter converts the voltage "el" (Vb)from the power-to-voltage conversion unit 11 into a digital value, andfurther converts the voltage VaH or the voltage VaL into a digitalvalue. In step S2, the CPU calculates digitized Vb/VaH (or, Vb/VaL), andfurther calculates digitized (Vb/VaH)² (or, (Vb/VaL)²). In step S3, theCPU calculates digitized Vb×(Vb/VaH)² (or, Vb×(Vb/VaL)²). In step S4,the CPU counts the result of the above calculation of the step S4 andobtains the total number of the count. In step S5, the CPU divides thetotal number of the count by a constant K. The constant K corresponds tothe rated input power explained in relation to the divider 4. That is,this calculation corresponds to that of the divider 4 in FIG. 2. In stepS6, the display 6 indicates the result of the division as the actualoperating time.

FIG. 6 is a schematic view of a hoist apparatus and a control boxincluding an actual operating time indicator according to the presentinvention. As explained above, the electric hoist apparatus has twomotors, i.e., the lifting motor for lifting a load up/down and thetravelling motor for moving the hoist apparatus toward the traversedirection of the beam. The control box has selection buttons, i.e.,"up", "down", "high" and "low" each of which is manually operated by anoperator. Further, the control box includes the display used as theactual operating time indicater according to the present invention.

We claim:
 1. An actual operating time indicator, comprising:a liftingmotor (M) for lifting a load (L) up/down; a power detection means (1)for detecting an input power (W) based on a current (A) and a voltage(V) supplied to the motor (M), and converting the input power (W) into afirst voltage (el) proportional to the input power (W); avoltage-to-periodic pulse conversion means (2) connected to the powerdetection means (1) for receiving the first voltage (el) and convertingthe first voltage (el) into the periodic pulse (f) proportional to thefirst voltage (el); a counter means (3) connected to thevoltage-to-periodic pulse conversion means (2) for counting andintegrating the periodic pulse (f) to obtain an integrated power; and adisplay (6) operatively connected to the counter means (3) forindicating the integrated power as an actual operating time (T) of themotor (M).
 2. An actual operating time indicator as claimed in claim 1,further comprising a divider (4) connected to the counter means (3) fordividing the integrated power by a power rating which is equivalent tothe input power per unit hour when lifting up a rated load.
 3. An actualoperating time indicator as claimed in claim 1, further comprising a BCDunit (5) operatively connected to the counter means (3) for converting abinary number into a decimal number to display the actual operating time(T) on the display unit (6).
 4. An actual operating time indicator,comprising:a lifting motor (M) for lifting a load (L) up/down; a powerdetection means (1') for detecting an input power (W) based on a current(A) and a voltage (V) supplied to the motor (M), converting the inputpower (W) into a first voltage (el, Vb) proportional to the input power(W), and further converting the first voltage (el) into a second voltage(e2) which is converted based on a predetermined formula defined by arelationship between a rated load and a life span of a mechanism; avoltage-to-periodic pulse conversion means (2) connected to the powerdetection means (1') for receiving the second voltage (e2) andconverting the second voltage (e2) into the periodic pulse (f)proportional to the second voltage (e2); a counter means (3) connectedto the voltage-to-periodic pulse conversion means (2) for counting andintegrating the periodic pulses (f) to obtain an integrated power; and adisplay (6) operatively connected to the counter means (3) forindicating the integrated power as an actual operating time (T) of themotor (M).
 5. An actual operating time indicator as claimed in claim 4,further comprising a divider (4) connected to the counter means (3) fordividing the integrated power by a power rating which is equivalent tothe power per unit hour when lifting up a rated load.
 6. An actualoperating time indicator as claimed in claim 4, further comprising a BCDunit (5) operatively connected to the counter means (3) for converting abinary number into a decimal number to display the actual operating timeon the display unit (6).
 7. An actual operating time indicator asclaimed in claim 4, wherein the predetermined formula is expressed byLh∝(1/P)^(n) where, Lh is a life span of a mechanism, P is a weight of aload, and n is an integer determined by a material of the mechanism. 8.An actual operating time indicator as claimed in claim 7, wherein,preferably, the integer "n" of the formula is given by a numeral "3" sothat the second voltage (e2) is determined based on the formula,

    Lh∝(1/P).sup.3


9. An actual operating time indicator as claimed in claim 4, wherein thepower detection means (1') includes an input voltage conversion unit(12) for obtaining the second voltage (e2), and the input voltageconversion unit (12) comprises:a first calculation unit (121) inputtingthe first voltage (Vb) and a rated voltage (VaH) which is given by thevoltage proportional to the rated input power of the lifting motor atthe high speed lifting operation, and calculating the formula (Vb/VaH)²; a second calculation unit (122) inputting the first voltage (Vb) and arated voltage (VaL) which is given by the voltage proportional to therated input power of the lifting motor at the low speed liftingoperation, and calculating the formula (Vb/VaL)² ; a selector (124) forselecting either an output of the first calculation unit (121) or anoutput of the second calculation unit (122); and a third calculationunit (123) inputting the first voltage (Vb) and either the voltage(Vb/VaH)² or (Vb/VaL)² calculating either the formula (Vb)×(Vb/VaH)², or(Vb)×(Vb/VaL)², and outputting the result of the above calculation asthe second voltage (e2).
 10. An actual operating time indicator,comprising:a lifting motor (M) for lifting a load (L) up/down; a powerdetection means (1) for detecting an input power (W) based on a current(A) and a voltage (V) supplied to the motor (M), and converting theinput power (W) into a first voltage (el) proportional to the inputpower (W); a microcomputer (M) connected to the power detection means(1) for receiving the first voltage (el) and outputting an integratedpower; and a display (6) connected to the microcomputer (M) indicatingthe integrated power as an actual operating time (T) of the motor (M).11. An actual operating time indicator as claimed in claim 10, whereinthe microcomputer (M) includes an analog-to-digital converter (A/D), aninput port, a central processing unit (CPU), a read only memory (ROM)for storing a basic program for calculation by the CPU, a random accessmemory (RAM) temporarily storing a result of the calculation by the CPU,a backup memory, and an output port;wherein, the A/D converter convertsthe first voltage (e1, Vb) into a digital value, and further converts arated voltage (VaH or VaL) into a digital value; the CPU calculates thefollowing; first, digitized Vb/VaH or Vb/VaL; second, digitized(Vb/VaH)² or (Vb/VaL)², and third, digitized Vb×(Vb/VaH)² orVb×(Vb/VaL)² ; the CPU counts the result of the calculation and obtainsthe total number of the count, and divides the total number of the countby a constant (K) which corresponds to a rated input power; and thedisplay (6) indicates the result of the division as the actual operatingtime (T);where, the rated voltage (VaH or VaL) is given by the voltageproportional to the rated input power of the lifting motor during thehigh (low) speed lifting operation.